Code review comment for lp:~tribaal/charms/precise/storage/refactor-mount-volume

These refactors look good and everything seems to work, but when running the moved tests (PYTHONPATH=hooks:$PYTHONPATH CHARM_DIR=`pwd` trial hooks/storage-provider.d/nfs/test_nfs_provider.py) had failures due to missing the setUp and imports that were in place in test_common_util.py, as well as the util.mount_volume -> util.{prepare,call}_volume_mount change.

I suggest fixing the tests and changing the `make test` target to use the PYTHONPATH modification to run these tests (I'd also put the tests in a top-level unit_tests folder so they're more easily discoverable, but that's up to you, as long as the `make test` target can run them).